+1 on Bike Flights. I have used them on several occasions. I also used the following as a template to make my own bike box:

https://www.crazyguyonabike.com/doc/...c_id=6740&v=3G

This is worthwhile if you can store the box for a return trip. It is sturdy enough to use for a couple of trips. It is pretty simple and inexpensive to make the internal wood frame. I suppose you could also make the frame out of pvc pipe, but I haven't tried that.

The fork crossbeam keeps the dropouts suspended, which makes it easier to protect the dropouts. I used a couple of discarded bike boxes to skin the frame. One benefit is that you can make it as big or small as you need. When using Bike Flights the box size, rather than the box weight (up to a certain weight), determines the shipping cost. Once you determine the box size you want, you can cram the box with camping gear, shoes, helmets etc.